Dual-fed mill



D.- coLE 1,986,103

DUAL FED MILL Jan. 1,-1935.

Filed April 18, 1932 lll Bnventor @ffornegs Patented Jan. 1, 1935 )UNITED STAT-Es vPari:

NT oFFicE ff l'jUL-FED '.L

David Cole, El Paso,r Tex. Y Application-April 1s, 1932, serial Nin-606,008

.prisesa cylindrical rod mill having large lhollow trunnions at each end thereof, through which the material is fed into the mill, and a central peripheral discharge .passage extending circumferyentially around the cylinderto provide egress for thefground material. f

lin the operation of revolving'grinding mills it -is recognizedthat van ideal mill is one in which the `'material is fed axially atone end thereof and 'discharged peripherally at the other endof the mill. The degree of grinding and flow gradient depend `largely on vthe'length of the mill, a short mill'eifecting coarseV grinding and'steep flow `gran dient while a long mill produces finer particles and a more gradual angle `between the inlet and outlet of the mill.. It is, of course, impractical to employ rods in a cylinder'having an open end since they would quickly work Aout vof the 'open end.

While mills having peripheral discharge opening have previously been proposed it has been necessary in all of these to provide screens in the cylinder Wall or screened partitions where grinding media other than rods are used. These parts quickly wear out and it is often necessary to dismantle the mill to effect repairs. Y

In the present invention the advantages of axial feed with peripheral discharge in a rod mill having no screen elements are utilized by combining, in eifect, two such mills with the open ends adjacent each other to form an annular discharge passage intermediate the closed ends of the mill. A suitable bridging ring, having openings therein, connects the two cylindrical portions of the mill.

There is also combined with the present mill feeding means designed to feed a constant sup-v ply of material at cach end of the mill. Dry material does not readily flow and must be fed directly and positively into the grinding chamber. A vibratory feeder is employed for this purpose.

The material is so fed that a definite relation of fngi e (ci. ssi-9*) section, vof la preferredembodiment ofthe invention.

Fig. 2 is a sectional view taken on line '2- 2 of Fis. 1-; and

Fig. 3 is a partial section taken on une afs v 5 of Fig". v1. l Y

In the drawing the y'mill comprisestwoallg'ned cylindrical sections 10, 10', having lianges'- 11'; to

which a bridging ring' 12 is'secui'ed. These sections are also provided with ange's 13, `to which *f heads 14, 14', are fastened. The' yhe'ads'have axial tubular extensions 15, forming intake openings, and trunnion portions 16, the latter vbeing surroundedfby bearing rings 17fsupported 'by roll# ers or bearings' 18 journaled in'fr'ames 19 at each end of the mill. Bridge ring `12 consistsy of continuous flanged sides 20 and a central annulusl21 connected by a plurality 'of spaced webs 22,' pref- `erably inclined with respect to radial planespassing through them, as indicated in Fig3, so that i relatively largeopenings 23 are provided "at each side of the annulus: A gear 24 vis suitably 'secured to lthe mill whereby the same 'is revolvedv by means Well'lknownin the art; Thus,- the several parts constitute a continuous cylindrical mill having a head and intake at each end anda central peripheral opening for discharge of ground material.

`Bolted rto the inner Walls of the cylinders are liners 25, having longitudinal ribs 26, and Wear plates 27 are fastened on the inside surface of heads 14, 14. The grinding is effected by the usual type of cylindrical metalrods 28 adapted to roll freely on the liners and on each other, and. having'a length substantially equal to that of the mill so that they bridge the central discharge openings and grind material to each side thereof.

At each end of the mill is a vibratory chute 29 supported by pitmen 31 and oscillated by an eccentric 32. This chute is rapidly oscillated to feed the dry material forwardly into the mill. Any suitable form of conveyor or hopper may be employed to deposit material on the chute. An outwardly flared annular member 33 is at. tached to each of the trunnions and cooperating with these members at each end of the mill is a stationary diaphragm 34 having an opening through which the chute projects. The diaphragm fits into the flared end to prevent dust from escaping from the grinding chamber through the trunnions.

Surrounding the central discharge passage is a dust-proof casing 35 having a suitableopening near the bottom thereof to permit passage of a belt conveyor 36 on to which ground material is discharged. A pipe 37 connects casing 35 with a suction fan whereby dust is drawn from the casing and subsequently recovered in a separator. The material carried away by conveyor 36 is screened and the oversize returned to chutes 29 by any convenient conveying means to be passed again through the grinding rods.

From the foregoing description of the apparatus and its operation it will be seen that the mill is capable of grinding dry material rapidly and that ingress andv egress of material is coordinated 'with rod capacity to insure maximum grinding eiciency without excessive disintegration of the material. The discharge openings are relatively large and capable of passing coarse as well as ne material for subsequent screening. AThis Vobviates the necessity of employing screens in the mill itself. The rods are so arranged that a substantial portion of the material introduced into the mill is ground in a comparatively short time and thedischarge passage, being centrally located, rapidly relieves the mill of material fed at each end thereof. f, i. I

The embodiment illustrated is a preferred one but it is intended that such changes as come within the principle of operation be made without departing fromA the ybroad idea involved.

, .What is claimed is: Y

l. A revoluble grinding mill comprising a cylinder having a peripheral discharge passage intermediate its'ends and-being imperforate except for said passage; a head at each end of said cylinder, at least one of said heads having an axial opening therein; a plurality of longitudinally disposed rods in said cylinder, said rods bridging said discharge passage and coacting with-the cylinder to grind material therein; and means for feeding material through said axial opening.

2. A revoluble grinding mill Ycomprising a cylinder. having a circumferential discharge .passage substantially mid-way itsv ends and being imperforate except for said passage; a head at each end of said cylinder having an axial opening therein; a plurality of longitudinally disposed rods in said cylinder, said rods bridging said discharge passage and coacting with the cylinder to grind material therein; and means for feeding material into each of said axial openings.

3. A revoluble grinding mill comprising a cylinder having a peripheral discharge passage midway its ends and being imperforate except for said passage; a head at each end of said cylinder having an axial opening therein; a plurality of longitudinally disposed rods in said cylinder, said rods bridging said discharge passage, extending substantially from one to the other of said heads and coacting'with the cylinder to grind material therein; and means for feeding material into each of said axial openings.

5l. A revoluble grinding mill comprising a pair of aligned cylinders; an annular bridging member connecting said cylinders, said bridging member having a plurality of openings therethrough; a head secured to the unconnected end of each cylinder, said head having an axial opening .therein; a plurality. of longitudinally disposed rods in said cylinder and extending substantially from one to the other of said heads; means for feeding material into each of said axial openings; and means for removing material discharged through the bridging member. f

5. A .revoluble grinding mill comprising a pair of `similar aligned cylinders; an annular bridging ring connecting said cylinders, said ring having continuous'flanged sides and spaced connecting webs to provide a substantially open circumferential opening between the connected vends of the cylinders; a head secured to the unconnected endvof each cylinder, said head having an axial opening therethrough; a plurality of loose longitudinally disposed rods in said cylinder and extending substantially from'one to the other of said heads; means for feeding material into each of said axial openings; and means disposed beneath said bridging ring for removing .material discharged through the ring.

DAVID COLE. 

